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Ceutics > 4. Disperse systems > Flashcards

4. Disperse systems Flashcards

0
Q

What is a suspension?

A

solid in a liquid

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1
Q

What makes up a dispersion?

A
  • a dispersed phase

- a continuous/dispersing phase

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2
Q

What is an emulsion?

A

liquid in a liquid

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3
Q

What is an aerosol?

A

solid or liquid in air

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4
Q

What is a coarse dispersion?

A
  • solute not dissolved and is visible
  • suspensions
  • emulsions
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5
Q

What is a fine dispersion?

A
  • solute not completely dissolved

- magmas and gels

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6
Q

what are colloidal dispersions?

A
  • solute not completely dissolved BUT not visible

- will scatter light

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7
Q

What are molecular solutions?

A
  • solute completely dissolved in solvent

- true solutions won’t scatter light

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8
Q

Why are disperse systems thermodynamically unstable systems?

A
  • larger particles have a greater tendency to separate from the dispersing phase
  • solids settle, liquids rise to top
  • must restore uniform distribution while moderate agitation for proper dosing
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9
Q

What are the advantages of suspensions?

A
  • ease of swallowing
  • flexibility of dose
  • bad tastes can be masked
  • drug may have increased stability
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10
Q

What are the disadvantages to suspensions?

A
  • physically unstable, will separate over time
  • if you don’t shake, dosing will be wrong
  • pt may not like mouth-feel (esp. if particle size if large)
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11
Q

What are the desirable attributes of a suspension?

A
  • should settle slowly and be re-dispersed with gentle shaking
  • particle size should remain fairly constant with shelf life
  • should pour readily and evenly
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12
Q

What are the parameters of sedimentation rate?

A
  • it’s a function of particle size
  • inverse function of viscosity (more viscous = slower settling)
  • small particle sizes can cake or agglomerate (stick together)
  • floccules can prevent caking
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13
Q

What are floccules?

A

a loose aggregation of particles

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14
Q

Why are floccules good?

A
  • they form higher sediment volumes than non-flocculated suspensions
  • loose structure = easy to re-disperse
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15
Q

How can you form floccules in suspension?

A

by adding surfactant or sometimes electrolytes

  • at specific concentrations they may neutralize surface charges
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16
Q

Why should a viscosity increasing agent be adding to suspensions with floccules?
What kind of viscosity agent should be used?

A
  • since the particles size is bigger (floccules), you need a higher viscosity to reduce settling

Want an agent that is:

  • higher viscosity at low shear rates (storage, after shaking, pouring)
  • low viscosity at high shear rates (shaking)
17
Q

Infants and neonates should have minimal exposure to:

A
  • preservatives
  • alcohol
  • propylene glycol
18
Q

What is the expiration date for aqueous extemporaneous solutions?

A

14 days in the refrigerator

  • to prevent microbial growth and increase stability
  • need to add preservatives if need for longer than 14 days
19
Q

What are the constituents of suspensions or structured vehicles?

A
  • active ingredient
  • wetting agent
  • suspending agent
  • flocculating agent
  • protective colloid
  • sweetener
  • preservative
  • buffer system
  • color agent
  • flavor agent
  • antifoaming agent
20
Q

What type of emulsion is more occlusive?

A

w/o

21
Q

What type of emulsion has better drug release?

A

o/w

22
Q

What is creaming?

A

In emulsions, when internal-phase droplets:

  • rise to the top (o/w)
  • sink to bottom (w/o)
23
Q

How can you stabilize an emulsion?

A
  • surfactants
  • hydrocolloids
  • solid particles
24
Q

What do surfactants do?

A
  • reduces repellent forces between phases
  • reduces attractive forces within each phase
  • breaks globules into smaller droplets

Can be:
anionic - sodium docusate, sodium oleate
non-ionin - spans and tweens
cationic - halides

25
Q

What do hydrocolloids stabilize emulsions?

A
  • provide protective multi-molecule layers around dispersed droplets
  • provide charge, droplets repel each other
  • may swell to increase viscosity
26
Q

How do solid particles stabilize an emulsion?

A
  • form layer around droplet and swell

- this increases viscosity and reduces attraction

27
Q

What is HLB?

What is it used for?

A

Hydrophilic-lipophilic balance

System designed to aid in determining the amount and type of emulsifier needed to produce stable emulsions

28
Q

What are the 3 methods of extemporaneous compounding?

A
  • continental
  • english
  • beaker
  • bottle
29
Q

What is the continental method?

A
  • primary emulsion of oil, water and emulsifier (4:2:1)
  • acacia used as gum emulsifier
  • gum and oil mixed, then all of water added with vigorous trituration
30
Q

What is the english method?

A
  • 4:2:1
  • gum mixed with water to make mucilage
  • oil added in parts with vigorous mixing
31
Q

What is the bottle method?

A
  • works best with low viscosity oil
  • 4:2:1
  • gum and oil added to bottle - mix vigorously
  • then water, mix vigorously
  • make an in situ soap
32
Q

What is the beaker method?

A
  • only 5% of synthetic emulsifier is needed
  • water soluble materials dissolved in water
  • oil soluble materials dissolved in oil
  • both solutions heating to 70 in water baths
  • internal phase added to external phase and mix until cooled to room temp
33
Q

Describe hydrophilic colloidal dispersions.

A
  • like water, hydrate and swell to increase viscosity
  • may carry a charge, the charge keeps particles separated
  • quite stable with affinity between particles and continuous phase
34
Q

Describe hydrophobic colloidal dispersions.

A
  • less stable than hydrophilic (no interaction between colloid and continuous phase)
  • stabilize by developing attraction between colloid particles and continuous phase
  • can carry a charge, repulsive forces and brownian motion keeps colloids dispersed
  • addition of electrolyte may neutralize charge and cause settling
35
Q

What is a two-phase gel?

A

gel made with discrete particles

36
Q

What is a single-phase gel?

A

if large organic macromolecules are uniformly distributed with no apparent boundaries between the dispersed and continuous phase

37
Q

What type of auxillary label should be used on disperse systems?

A
  • shake well
  • refrigerate (if applicable)
  • external (if applicable)
38
Q

Why are disperse systems packaged in oversized containers?

A
  • to facilitate shaking
39
Q

What is the usual concentration of surfactants in disperse systems?

A

2-5%

ex. tween 80, span 20

40
Q

What will happen to a disperse system if a preservative is not used?

A
  • will only last 2 weeks with refrigeration
41
Q

What is the ingredient function of:

  • hydrochlorothiazide
  • methycellulose
  • citric acid
  • sodium benzoate
  • aspartame
  • orange flavor
  • purified water
A
  • API
  • suspending agent
  • pH adjuster
  • preservative
  • sweetener
  • flavor
  • vehicle

Ceutics (8 decks)

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